This invention relates generally to gas turbine engines and, more particularly, to an engine control system for a turbofan engine having variable stators and a fuel control system responsive to fan speed.
The invention herein described was made in the perfomrance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 USC 2457).
Historically, commercially flights have been characterized by takeoffs and landings which are relatively slow and time consuming and by intermediate relatively high speed cruising. Because of the great distances traveled, the cruise time made up the major portion of the total trip time, and rapid takeoffs and landings were not considered necessary. Further, for safety purposes it has been desirable to operate with long runways and relatively gradual takeoffs and landings.
Present-day requirements have been somewhat modified from the past in that there is now more concern about the noise and air polution which exists in airport vicinities because of the high-thrust, relatively inefficient engine operation during takeoffs and landings. Further, there now appears to be a greater need for short haul transport service. Accordingly, there is an effort in the industry to shorten the takeoff and landing periods of operation by aircraft improvisations and by engine design changes. One of the critical points of this manner of operation is that, when you are making a landing at a large descent rate and a go-around maneuver is suddenly necessary, the thrust must be quickly increased from a level of approximately one-half to two-thirds of takeoff thrust to full takeoff thrust in a very short period of time (approximately one second). Present aircraft engines do not provide this capability, primarily because of the high inertia of the compressor.
It is therefore an object of the present invention to provide an aircraft engine which facilitates rapid takeoffs and landings.
Another object of the present invention is the provision in an aircraft for negotiating a go-around maneuver when making a landing approach at a large descent rate.
Yet another object of the present invention is the provision in an aircraft engine for quickly accelerating from an approach thrust level to a takeoff thrust level.
Yet another object of the present invention is the provision in an aircraft engine for overcoming the problem of high compressor inertia when negotiating a go-around maneuver.
Still another object of the present invention is the provision in an aircraft engine for a control system which is effective in use and economical to manufacture.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.